Excavating machinery for the formation of ditches, trenches and the like have generally comprised a vehicular chassis adapted to be propelled on the ground ahead of a trench or ditch to be advanced or cut therein, and a cutting head which can be lowered from this chassis into the ground and drawn by a backward movement of the vehicular structure therealong to cut the trench in the ground.
Reference may be made to German patent publication (Auslegeschrift) No. DE-AS 27 00 950 (see also U.S. patent application Ser. No. 868,733, now U.S. Pat. No. 4,173,836, issued Nov. 13, 1979, and the art of record therein) which describes a ditching or trenching machine which has been found to be highly effective and which comprises a vehicular body which is propelled along the ground on tracks.
The rotary milling-type cutter of this machine is mounted on a cutting head or carrier which is articulated, in turn, to a boom, arm or outrigger swingable about horizontal and vertical axes to lower the cutting head into the ground and thereafter draw the cutting head along the path of the trench to be excavated upon movement of the vehicle rearwardly in the manner of a backhoe.
As noted, such machines have been found to be highly effective but, when deep trenches are to be excavated, especially large and expensive machines must be provided, and there is considerable concern regarding the stability of the machine because the reaction forces are applied over exceptionally long lever arms and distances to a support structure located well above and in advance of the face of the trench to be excavated.
Another difficulty with suuch systems, especially when deep excavations are to be made, is that removal of the detritus poses a problem.
It is customary, therefore, when deep and large trenches are to be excavated, to use a machine of the type described to break loose the advancing face of the trench wile another excavator, e.g. a bucket or backhoe excavator, is employed to lift the detritus from the trench.